Theory question 108
Animal Health(a) With the aid of an annotated diagram, describe the life cycle of the liver-fluke (Fasciola hepatica).
(b) Explain how you will prevent the liver-fluke from completing its life cycle in the field.
(c) List three effects of lice on animal production.
Show the model answer
(a) Annotated diagram: adult flukes in the bile ducts of sheep/cattle lay eggs that pass out in faeces; in water eggs hatch into miracidia; miracidia enter a water snail (intermediate host) and multiply (sporocysts, rediae); cercariae leave the snail and encyst on grass as metacercariae; animals eat infected grass; young flukes bore through the gut wall into the liver and settle in the bile ducts
(b) Any: drain wet, marshy pastures; kill snails with molluscicides (e.g. copper sulphate) or ducks; fence off wet areas; rotational grazing; deworm animals regularly with flukicides; do not graze animals near water; dispose of dung properly
(c) Any three: irritation, restlessness and loss of rest; loss of appetite and weight; damage to skin, wool and hide; anaemia; lower milk and egg production; spread diseases
Show both hosts and every larval stage in the diagram.